I agree that the 6.4L and 4.10s is the sweet spot for the Ram HD gassers. I have a friend with 5.7L 2500. He is very happy with it. I think most of his towing is around 5000 - 6000 lbs. I dunno about his mileage. My 1500 has the 5.7L and gets around 9 - 10 mpg when towing. Even though I've had it almost 3 years and 36k miles, I'm still learning the empty mileage. On winter 87 octane, I'm getting just under 14 mpg mixed city/highway. Recently refilled half a tank with 91 octane ethanol free and my mileage jumped up to near 16, and performance is wayyy better. My figures are from the lie-o-meter.